With an increase in traffic flowing into a network, a network device has been growing in size and improving in performance, and the amount of power consumption and an operating cost (referred to as a cost inclusive of the amount of power consumption and the operating cost) has been increasing.
In the meantime, redundant lines and devices are arranged to accommodate traffic in many cases in a current network. With an optimum arrangement of lines and devices, cost reductions such as power saving and the like of the entire network can be expected. However, a suitable arrangement of lines and devices differs depending on a traffic transfer state (path). Therefore, it is important to comprehensively consider an arrangement of a traffic route (path), lines and devices, and the like when a power-saving network configuration is derived.
Incidentally, there is a problem that a network design in consideration of a dependency among diverse design elements (route, line, device) is difficult with a conventional manual design. Therefore, a technique for automatically designing a network configuration that minimizes power (or cost) by systematizing a design process in consideration of a correlation among the design elements is demanded.
As a conventional method of making a network design including a route, there is an incremental design method of accommodating each path demand (a demand for laying a communication route between desired sites with a desired capacity). A MAX-PACK method of determining a traffic transfer route so that an expansion (line addition) cost is minimized is normally known.
This conventional method does not lose generality, also enabling a route design that minimizes power even if cost (the amount of money) is replaced with the amount of power consumption.
These methods mainly aim at minimizing a cost (the amount of money or power) of each added line (port) as an expansion (line addition) cost. However, there are not so many actual network devices that can be added in units of ports.
By way of example, for a box type device implemented by incorporating a port group of each line type into a housing, design measures are taken such that
the device is left unchanged if the available ports of the device remain, or
the device is replaced if the number of ports of the device is insufficient as a result of adding a port when a path is accommodated.
Similarly, for a chassis type device implemented by handling a port group of each line type as a network card (package), design measures are taken such that
the device is left unchanged if the available ports of the network card remain, or
the device is replaced with a network card that can accommodate a corresponding number of ports if the number of ports of the network card is insufficient
as a result of adding a port when a path is accommodated.
This means that the cost is not determined in units of ports but in units of devices or packages including a port group.
Accordingly, with a conventional design of a minimum cost path based on cost per port, only a change of cost (power or the amount of money) estimated by accumulating cost of each port can be determined, and a possible change of cost (power or the amount of money) incurred by arranging a device/package in an actual network cannot be suitably judged.
For example, also from the viewpoint of the amount of power consumption, the amount of power consumption of an actual device or package does not vary depending on a use state of a port, and a certain amount of power is consumed. Therefore, a change of an actual cost (power) cannot be estimated by accumulating a cost of each port.
FIGS. 1 and 2 are explanatory views of the problem of the conventional method.
A design example to which the conventional method is applied is described. As illustrated in FIG. 1, a design of a path and a line (port) when a path demand is given under a condition that a device with low cost (power) per port and a device with high cost per port are respectively arranged on an upper route and a lower route is considered. At this time, the conventional design in consideration of only cost per port produces results such that the upper route is selected and a port is simply added to an upper node.
In the meantime, a case where actual box type devices A and B illustrated in FIG. 2 are assumed by taking FIG. 1 as an example and a cost (power) per port of each of the devices is estimated as follows
device A: 5/12=0.42 (cost/ports)
device B: 20/24=0.83 (cost/ports)
is considered.
Also at this time, a result such that the upper path is selected is produced with the conventional design based on a cost per port similarly to FIG. 1. Actually, however, a case where the minimum cost (power) cannot be achieved is considered as follows.
For example, in a case where the number of remaining ports is zero in the device A and the number of remaining ports is too many in the device B when a port is designed to be added at the time of path demand accommodation,
1. if the upper route is allocated, the device A needs to be replaced with the device B, leading to an increase in cost (power) incurred by replacing the device.
2. if the route goes through the device B with higher cost per port, the device B does not need to be changed because the number of ports is too many. Therefore, the cost (power) does not change.
Accordingly, assuming such an actual environment, a route selection and a line/device arrangement, which minimize a cost (power), cannot be implemented only based on a conventional cost determination made in units of ports.